HYDROXYLAMINE AND METHOXYAMINE MUTAGENESIS - TAUTOMERIC EQUILIBRIUM OF THE PROMUTAGENIC, N-6-METHOXYADENOSINE IN SOLVENTS OF DIFFERENT POLARITIES

  • 1 January 1984
    • journal article
    • research article
    • Vol. 31  (1) , 49-64
Abstract
UV and IR spectroscopy were applied to a study of the tautomeric equilibrium, in solvents of varying polarities and differing hydrogen bond donor-acceptor properties, of the promutagenic analog N6-methoxyadenosine, the product of the reaction of the mutagen methoxyamine with adenosine. In the non-polar solvent CCl4, the analog is predominantly in the amino form with KT [tautomeric constant] .apprx. 10. On transfer from CCl4 to chloroform, dimethyl sulfoxide and water, the equilibrium is shifted stepwise towards the imino form, attaining a KT .apprx. 10 in favor of the imino species in aqueous medium. Both the UV and, particularly, the IR spectra exhibit 2 sets of absorption bands which were assigned to the respective tautomers in dynamic equilibrium with each other. The significance of the foregoing results in the mechanism of hydroxylamine (and methoxyamine) mutagenesis is considered. Base pairing of each tautomeric species is significantly dependent on the conformation of the exocyclic N6-methoxy group. IR-spectroscopy provides data which both supplement and extend those obtained by NMR spectroscopy, under conditions where application of the latter is technically limited.

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